The present invention relates to a novel chemical-sensitization photoresist composition or, more particularly, to a chemical-sensitization photoresist composition capable of giving a patterned resist layer with high contrast, high pattern resolution and high photosensitivity as well as an excellent cross sectional profile of the patterned resist layer and also having an advantage in respect of the stability of the latent image before development after pattern-wise exposure to actinic rays.
In the photolithographic patterning technology for the manufacture of various kinds of semiconductor devices, liquid crystal display panels and the like by utilizing a photoresist composition, it is a remarkable trend in recent years that so-called chemical-sensitization photoresist compositions are acquiring more and more prevalence among various types of photoresist compositions. The chemical-sensitization photoresist composition here implied is a photoresist composition containing an chemical agent capable of releasing an acid by the irradiation with actinic rays while the thus generated acid has a catalytic activity on the radiation-induced changes in the solubility of the resinous ingredient in an aqueous alkaline developer solution so that the photoresist composition has a high photosensitivity with a relatively small exposure dose.
Chemical-sensitization photoresist compositions can be classified into two types including the positive-working photoresist compositions and negative-working photoresist compositions depending on the solubility change of the resist layer in an alkaline developer solution caused by the irradiation with actinic rays. The basic ingredients of a chemical-sensitization photoresist composition include the above mentioned radiation-sensitive acid-generating agent and a film-forming resinous ingredient which causes a change of the solubility in an aqueous alkaline developer solution by interacting with the acid released from the acid-generating agent by the pattern-wise exposure of the resist layer to actinic rays.
The formulations of the chemical-sensitization positive- and negative-working photoresist compositions are different in the film-forming resinous ingredients. Namely, the chemical-sensitization positive-working photoresist composition usually contains, as the film-forming resinous ingredient, a polyhydroxystyrene resin of which a part of the hydroxyl groups are substituted for the hydroxyl hydrogen atoms by solubility-reducing protective groups such as tert-butoxycarbonyl groups, tetrahydropyranyl groups and the like while the film-forming resinous ingredient in the chemical-sensitization negative-working photoresist composition is usually a combination of a polyhydroxystyrene resin, which is optionally substituted for a part of the hydroxyl hydrogen atoms by the solubility-reducing protective groups mentioned above, or a novolak resin with an acid-crosslinkable agent such as melamine resins, urea resins and the like.
Various attempts and proposals have been made heretofore for selection of the radiation-sensitive acid-generating agent used in the above described chemical-sensitization photoresist compositions including, for example, certain diazomethane compounds disclosed in Japanese Patent Kokai 3-103854, 4-210960 and 4-217249.
It is also known in the prior art to use an acid-generating agent which is a compound having an acid-dissociable group in the molecule as disclosed in Japanese Patent Kokai 64-26550 and 64-35433. The acid-generating compounds disclosed there, however, are limited to onium salt compounds. A chemical-sensitization photoresist composition formulated with such an onium salt compound as the acid-generating agent has a disadvantage that the performance thereof is subject to the adverse influences of standing waves of the exposure light so that the patterned resist layer formed therefrom sometimes has wavy side lines of the cross sectional profile. The above mentioned Japanese Patent Kokai 3-103854, 4-210960 and 4-217249 also teach use of a certain diazomethane compound as the acid-generating agent and, among these diazomethane compounds, the non-aromatic diazomethane compounds, such as bis(cyclohexylsulfonyl) diazomethane, in particular, are highly transparent to excimer laser beams of 248 nm wavelength and capable of giving a high pattern resolution though with disadvantages in respect of the relatively low efficiency for the generation of an acid as well as a low patterning contrast since the acid generated therefrom is a weak acid so that the photoresist composition formulated therewith can hardly exhibit a high photosensitivity. In addition, the resist layer obtained from a resist composition formulated with such a diazomethane compound as the acid-generating agent is disadvantageous in respect of the relatively low stability of the latent image, which is formed by the pattern-wise exposure to light, before the post-exposure baking treatment.